1. Field of the Invention
The present invention relates to a disk player for effecting the reproduction, recording, or deleting of an optical disk or a magnetic disk (hereafter referred to as the disk) such as a DVD.
2. Description of the Related Art
Conventionally, as a technique concerning a disk player, one such as shown in a JP-A-9-293369 is known. A description will be given of one such example with reference to FIGS. 5 to 9. In this disk player, a synthetic resin-made drive chassis 2 is disposed in a housing 1 in such a manner as to be movable in upward and downward directions a and b by means of a pair of pivot shafts 2a respectively provided projectingly on rear portions of both side surfaces thereof. A camshaft 2b provided projectingly on a front surface of the drive chassis 2 is fitted in a cam hole 3a of a cam plate 3 which is movable in leftward and rightward directions c and d. A deck 2A is integrally formed on a front side of the drive chassis 2, while an accommodating recess 2B is formed on a side located rearwardly of the deck 2A of the drive chassis 2. One side edge of the accommodating recess 2B is formed as a guide rail 4 extending in backward and forward directions e and f from a rear end portion of the drive chassis 2 to the deck 2A. As a front end 5a of a guide shaft 5 is fitted in a fixing hole 6 of the deck 2A, and a rear end 5b of the guide shaft 5 is fixed to the rear end portion of the drive chassis 2 by means of a screw 7, the guide shaft 5 is disposed on the other side edge side of the accommodating recess 2B in parallel with the guide rail 4. It should be noted that although a multiplicity of holes are formed in the deck 2A, as required, the illustration of the holes is omitted to facilitate the explanation.
As shown in FIGS. 5 to 7, an optical pick up 9 made up of a synthetic resin-made base 9A and a pickup body 9B disposed on the base 9A is disposed in the accommodating recess 2B. The pickup body 9B includes an actuator base 10 screwed down onto the base 9A; a lens holder 12 having an objective lens OL and fitted in a supporting shaft 11 provided uprightly on a bottom plate of the actuator base 10; a focusing coil 13 and a tracking coil 14 installed on the lens holder 12; and a pair of permanent magnets 15 opposing each other with the lens holder 12 interposed therebetween. As the lens holder 12 is moved in focusing directions g and h by exciting the focusing coil 13 at a predetermined input frequency, and the tracking coil 14 is exited at a predetermined input frequency, the lens holder 12 is moved in tracking directions i and j.
As shown in FIGS. 5 to 8, a pair of outwardly expanding and inclined inner side surfaces 18a of an annular guide groove 18, which is formed in an outer peripheral surface of a guide roller 17 pivotally secured to one end portion of the base 9A, are engaged with the guide rail 4. At the same time, the guide shaft 5 is fitted in a bearing hole 19a of each of a front and rear pair of bearing portions integrally provided projectingly on the other end portion of the base 9A. A pinion 21 is threadedly engaged with a rack 20 connected to the other end portion of the base 9A. As the pinion 21 is rotated forwardly or reversely through a gear mechanism 23 by a feed motor 22, the optical pick up 9 is reciprocatingly moved in the backward and forward directions e and f along the guide rail 4 and the guide shaft 5 by means of the rack 20.
As shown in FIGS. 5 and 9, a recessed groove 25 communicating with the accommodating recess 2B is formed in the center of a rear portion of the deck 2A. A spindle motor 26 is fixed in the recessed groove 25, and a turntable 27 for mounting a disk D is secured on a rotating shaft 26a of the spindle motor 26.
To describe the operating procedure, as the cam plate 3 is slid in the rightward direction d (or the leftward direction c), the drive chassis 2 is moved in the upward directions a about the pivot shaft 2a by means of the cam hole 3a and the cam shaft 2b so as to be set in a horizontal state, the disk D is thereby mounted on the turntable 27 (FIG. 7). The disk D is rotated at high speed by the spindle motor 26, and the optical pick up 9 is reciprocatingly moved in the backward and forward directions e and f along the guide rail 4 and the guide shaft 5. The lens holder 12 is moved in the focusing directions g and h and the tracking directions i and j by exciting the focusing coil 13 and the tracking coil 14 at the predetermined input frequencies. Further, as laser light is projected onto the disk D through the objective lens OL, information recorded on the disk D is read.
With the above-described conventional construction, the one side edge of the accommodating recess 2B formed in the drive chassis 2 is used jointly as the guide rail 4 to attain a cost reduction, and there is an advantage in that as compared with a case where two guide shafts 5 are used, the number of parts is small, so that this arrangement is economical. However, a slight gap is likely to occur between the guide rail 4 and the annular guide groove 18 of the guide roller 17 engaging therewith. As a result of the occurrence of the gap, when the lens holder 12 is moved in the focusing directions g and h by exciting the focusing coil 13, the optical pick up 9 is vibrated in upward and downward directions k and m (see FIG. 6) about the guide shaft 5 owing to that movement. This vibration is transmitted from the guide rail 4 (and the guide shaft 5) to the turntable 27 through the deck 2A and the spindle motor 26, causing the disk D on the turntable 27 to vibrate infinitesimally.
As shown in FIG. 7, when the present inventor examined the infinitesimal vibration (vibration acceleration) of a central portion of the disk D by an acceleration pickup 29, the infinitesimal vibration was as shown at a phantom line G in FIG. 10. It was found that the disturbance of the focus servo characteristic was large particularly in a normal working range α (1,300 to 2,100 Hz) of the focusing coil 13.
In the above-described construction, since the disturbance of the focus servo characteristic is large, the focusing of the objective lens OL with respect to the disk D takes time, and the reading speed is therefore delayed.